1. Field of the Invention
The present invention relates to a coating apparatus suitable for applying a high voltage to a conductive coating material such as a water base coating material to perform coating. More particularly, it relates to an apparatus for supplying a non-conductive coating material and a conductive coating material.
2. Description of the Related Art
A water base coating material can be readily disposed since it does not contain an organic solvent, and it is easy on an environment. Further, it does not contain a dangerous material such as an organic solvent, and hence it is excellent in prevention of fire accidents. Therefore, there is increased a demand as an intermediate coating material or a finish base coating material in place of or together with an organic solvent base coating material.
In case of applying a high voltage to such a water base coating material to perform electrostatic coating, an external application system or an insulation mechanism for a coating circuit (which will be hereinafter referred to as a voltage block system) must be employed, in contrast to the organic solvent base coating material (Japanese Patent No. 2790153).
An external application system applies a voltage from an external electrode to coating particles which have been sprayed and atomized by a coating machine so that the coating particles are charged with electricity. Since the coating particles are not contact-charged in a coating circuit, the electricity scarcely flows through the coating material.
However, the external application system has the worse coating deposition efficiency than that of the voltage block system, which leads to a problem that an amount of coating material to be used is increased as much as approximately 10%. Further, a coating gun is apt to splotched in principle, and a defect such as irregularity of a coating material consequently tends to occur. Thus, a frequency of cleaning the coating gun must be increased, which may lower the productivity.
On the other hand, as a conventional voltage block system, there is known an intermediate coating tank insulation system which lifts an intermediate coating tank set on a booth side by an insulation mounting so that an area from the coating machine to the intermediate coating tank becomes a charging range.
However, when a number of paint colors is large, a large space is required on the booth side. Further, when color change is frequently performed or an amount of coating material to be used is large, the working property is deteriorated.
In view of the above-described problems in the prior art, an object of the present invention is to provide an inexpensive coating apparatus which is superior in the insulating property and the color change working property and can be applied to both a conductive coating material and a non-conductive coating material.
To achieve this aim, there is provided a coating apparatus comprising: a coating gun to which a voltage is applied; a coating pipe for leading a coating material to the coating gun; a piston provided in the coating pipe so as to be capable of water-tightly sliding; and a drive portion for moving the piston in the coating pipe, the coating material being injected into a front part of the piston and the piston being moved toward the coating gun at the time of coating.
Further, to achieve the above aim, there is provided a coating apparatus comprising: a coating gun to which a voltage is applied; a coating pipe for leading a coating material to the coating gun; a cylinder provided in the middle of the coating pipe; a piston provided in the cylinder so as to be capable of water-tightly sliding; and a drive portion for moving the piston in the cylinder, the coating material being injected into a front part of the piston and the piston being moved toward the coating gun at the time of coating.
Moreover, to achieve the above aim, there is provided a coating apparatus comprising; a coating gun to which a voltage is applied; a first coating pipe for leading a coating material to the coating gun; a first piston provided in the first coating pipe so as to be capable of water-tightly sliding; a first drive portion for moving the first piston in the first coating pipe; a second coating pipe for supplying the coating material to a front part of the first piston; a second piston provided in the second coating pipe so as to be capable of water-tightly sliding; a second drive portion for moving the second piston in the second coating pipe; and an opening/closing valve provided to a connection portion between the first coating pipe and the second coating pipe, the coating material being injected to a front part of the second piston at the time of coating, the second piston and the first piston being moved toward the coating gun.
Furthermore, to achieve the above aim, there is provided a coating apparatus comprising: a coating gun to which a voltage is applied; a coating pipe for leading a mixed coating material containing at least two kinds of coating materials to the coating gun; a piston provided in the coating pipe so as to be capable of water-tightly sliding; a drive portion for moving the piston in the coating pipe; and a mixer for mixing the at least two kinds of coating materials to supply the mixed coating material to the coating pipe.
In addition, to achieve the above aim, there is provided a coating apparatus comprising: a coating gun which has at least two trigger valves and to which a voltage is applied; at least two coating pipes for respectively leading the at least two kinds of coating materials to the trigger valves of the coating gun; at least two pistons provided in the at least two coating pipes so as to be capable of water-tightly sliding; and at least two drive portions for respectively moving the at least two pistons in the coating pipes.
Further, to achieve the above aim, there is provided a coating apparatus comprising: a coating gun to which a voltage is applied; a mixer for mixing at least two kinds of coating materials and supplying an obtained mixed coating material to the coating gun; at least two coating pipes for leading the at least two kinds of coating materials to the mixer; at least two pistons provided in the at least two coating pipes so as to be capable of water-tightly sliding; and at least two drive portions for respectively moving the at least two pistons in the coating pipes.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.